Decatur Electronics Genesis VP Directional User Manual - Page 13
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As the angle between the beam of the antenna and the targeted
motor vehicle increases, the displayed speed decreases Ideally,
an angle of zero degrees (0°) is preferable, because the displayed
speed is the actual targeted motor vehicle speed However, in all
uses of police radar, the radar device is always at a slight angle to
the targeted motor vehicle to avoid collisions
Radar
An angle between the antenna and the target vehicle causes the cosine efect
The following table shows the efect that an increasing angle has
on a displayed speed
0°
1°
3°
Actual
Speed
50 km/h
50 49 49 49 49
65 km/h
65 64 64 64 64
80 km/h
80 79 79 79 79
90 km/h
90 89 89 89 88
100 km/h
100 99 99 99 98
110 km/h
110 109 109 109 108
Actual and displayed speeds at diferent antenna-to-target angles
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Velocity
Vector
Angle
Figure 5.2.1a
Horizontal Angle Degrees
5° 10° 15° 20° 30°
45° 60° 90°
Displayed speed:
48
46
43
35
25
62
61
56
45
32
77
74
69
56
40
86
84
77
63
45
96
93
86
70
50
106
103
95
77
55
Table 5.2.1b
25/Aug/2010
Small angles (less than 10°) have little efect on accuracy As the
angle increases, the displayed speed decreases At 90°, the target
speed is 0—grossly incorrect Cosine Efect will always result in a
target speed being displayed that is less than the actual speed of
the moving motor vehicle, which will always be advantageous to
the motorist
5.2.2 Fan Interference
Fan interference is the most common form of interference that you
are likely to experience It is caused when the radar measures the
speed of the vehicle blower fan Changing the fan speed causes a
proportional change in the display speed
5.2.3 Electromagnetic Interference (EMI)
Operating electric motors can produce EMI With the DSP
algorithms the Genesis-VPD has eliminated this
5.2.4 Feedback Interference
When the radar beam is directed at computer screens, streetlights,
and other electronic devices, it can display spurious speeds To
correct the interference, relocate the radar gun antenna
5.2.5 Multi-Path Beam Cancellation
The Genesis-VPD is immune from multi-path cancellation
5.2.6 Radio Frequency Interference (RFI)
The Genesis-VPD contains an RFI detection circuit that detects
excess radio frequency energy When stray radio frequency energy
reaches an excessive level, the system displays an RFI message
0
and stops processing and displaying speeds The system resumes
0
normal operation when the RFI condition no longer exists At that
0
time, any locked speeds will display again
0
0
5.2.7 Scanning
0
The Genesis-VPD is designed to be used while attached to a solid
mount or hand-held in a steady position Moving or "scanning" the
antenna past stationary objects can cause the system to detect
25/Aug/2010
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